Bromate suppression

ABSTRACT

A apparatus and method for killing microorganisms in a body of water that has been treated with ozone in the presence of bromide ions with the method comprising the steps of carrying out the ozonization of a body of water in the presence of bromide ions, adding a metal ion donor to the body of water, and adding a hypobromite ion scavenger to the body of water to interact with the metal ion donor to enhance a metal ion concentration in the body of water while suppressing the oxidization of the bromide by the Ozone to produce bromate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 12/386,074filed Apr. 14, 2009 titled BROMATE SUPPRESSION (pending), which claimspriority to Provisional Application Ser. No. 61/126,136; filed on May 1,2008; titled ION ENHANCEMENT AND BROMATE.

FIELD OF THE INVENTION

This invention relates generally to water treatment and morespecifically, to the combination of a metal ion donor, bromide ion donorand a source of a hypobromite ion scavenger such as dimethylhydantoin(DMH) to enhance the effectiveness of the metal ion donor in killmicroorganisms in a body of water that has been treated with ozone whileeliminating or reducing the production a bromate.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

REFERENCE TO A MICROFICHE APPENDIX

None

BACKGROUND OF THE INVENTION

The concept of treating water with a source of metallic ions to killbacteria in a body of water is known in the art. A metallic ion such asa silver ion is an effective bactericide for a body of water includingrecreational water such as swimming pools, spas, jetted tubs or the likeand is a preferred material because it is generally easier and safer touse when compared to other known bactericides or algaecides. A furtheradvantage of using silver ion as a bactericide is that silver ionminimizes the need for pH adjustment to the body of water. However, ifthe concentration of metallic ions such as silver ions in a body ofwater is too low the ability to kill microorganisms is reduced or lost.Conversely, if the concentration of metallic ions such as silver ions istoo high it can potentially lead to undesired effects such as causingthe user's skin to turn yellow and staining clothes. Thus when silverion is used as a disinfectant in a body of water one generally want tomaintain the concentration of the silver ion in a range that iseffective killing microorganisms without leading to the undesiredeffects associated with higher levels of silver ions.

Traditionally, the sources of metallic ions used to kill bacteria inrecreational water have been limited to metallic ion donors that arereadily soluble in the recreational water in order to maintain aneffective concentration of the biocides in the body of water. Silverchloride (AgCl), for example, has been a commonly used bactericide forreleasing silver ions into the body of water to effectively killmicroorganisms. Sodium bromide has also been known to be used withsilver chloride to provide an additional and alternative waterdisinfection system.

One of the problems associated with the use of silver for killingmicroorganisms is that silver has a tendency to complex with othercompounds and become increasingly insoluble thereby reducing theeffective microorganisms killing ability of the silver. For example, itwould not be anticipated that silver chloride when used in combinationwith sodium bromide would be an effective prolonged disinfectant systembecause of the combination's tendency to form insoluble silver bromidecrystals, which are not believed to be biologically active in aqueousenvironments.

The use of Ozone (O₃) for water disinfection is also known in the art.Examples of current Ozone uses include treatment of recreational watersand treatment of wastewater. Use of Ozone for water disinfection isgenerally preferred because it is considered to be anenvironmentally-friendly biocide that produces no hazardous by-productswhen used alone. However, Ozone generally cannot be used alone as aneffective prolonged bactericide for a body of water includingrecreational waters such as swimming pools, spas, jetted tubs or thelike because Ozone tends to be unstable in water especially at elevatedpH, and it is readily volatilized from water.

To overcome the problems associated with the use of Ozone whileretaining the benefits of Ozone usage, it is also known in the art topost-treat water that has been treated with Ozone with a more stablebiocide. For example, bromine displays excellent biocidal propertieseven at elevated pH where Ozone is unstable, and is less prone tovolatilization from water than Ozone. The use of a source of brominesuch as sodium bromide to post-treated water that has gone through theozonization process is advantageous in that sodium bromide normallyrequires a strong oxidizer such as ozone in order to transform sodiumbromide into the bromine's biocidially active form. The benefit of thedual use of Ozone and a more stable biocide such as bromine is that useof the Ozone requires less amounts of bromine to be used in order tomaintain effective levels of water disinfection.

Although the dual use of Ozone and bromide is effective at maintainingan effective level of water disinfection, the problem associated withthe dual use of Ozone and bromide is that the bromides contained in thewater are partly oxidized by the Ozone to produce bromate, which ishighly undesirable in that bromate, in higher concentrations, is a knowncarcinogenic.

To solve the above problems, it has been discovered that theintroduction of small amounts of hydantoins to a body of water that hasbeen treated with Ozone and containing silver ion and bromide ionsresults in the silver ions forming a complex with the hydantoins andremain soluble to a higher degree thereby retaining the silver'santimicrobial activity compared to the use of silver ion and bromideions alone. It has also been determined that the hydantoins functions tosuppress the oxidization of the bromide by the Ozone to produce bromate.

The present invention includes a device and method for using metal iondonors and bromide ion donors in combination with hydantoins includingunhalogenated hydantoins such as 5,5-dimethylhydantoin (hereinafter“DMH”) in a body of water to enhance a concentration of the metal ionsin the body of water or to enhance the solubility of metal ions fromother metal ion donors to retain the silver's antimicrobial activity inthe water while suppressing the oxidization of the bromide by the Ozoneto produce bromate.

SUMMARY OF THE INVENTION

Briefly, the present invention comprises a method and a device forkilling microorganisms in a body of water that has been treated withozone in the presence of bromide ions. The apparatus comprises adispenser with a first housing having a water accessible compartmentcontaining a source of a hypobromite ion scavenger for releasing thehypobromite ion scavenger when contacted by the body of water and asecond housing having a water accessible compartment containing a metalion donor for releasing metal ions when contacted by the body of water.The dispenser may also include a third housing having a water accessiblecompartment containing a bromide ion donor for releasing bromide ionswhen contacted by the body of water.

The method includes the steps of carrying out the ozonization of a bodyof water in the presence of bromide ions, adding a metal ion donor tothe body of water, and adding a hypobromite ion scavenger to the body ofwater to interact with the metal ion donor to enhance a metal ionconcentration in the body of water while suppressing the oxidization ofthe bromide by the Ozone to prevent or reduce the production of bromate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a table containing test results for bromide and dissolvedsilver concentration for a Spa Study 1;

FIG. 2 shows a table containing test results for bromide and dissolvedsilver concentration for a Spa Study 2;

FIG. 3 shows a table containing test results for bromide and dissolvedsilver concentration for a Spa Study 3;

FIG. 4 shows a dispenser having a housing containing a compartmentcontaining DMH and a silver ion donor comprising silver chloridetherein; and

FIG. 5 shows a dispenser having a first housing containing DMH and asecond housing containing silver ion donor comprising silver chloride,and a third housing containing a bromide ion donor therein.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hydantoin structures are known complexing agents in silver-platingprocesses (R. J. Morrissey, U.S. Patent Application Publication no.2005/0183961). Studies performed by the inventor have demonstrated thathalogenerated hydantoins such as Bromochlorodimethylhydantoin (BCDMH)and Dichlorodimethylhydatoin (DCDMH) tend to increase levels ofdissolved silver. While not fully understood it is believed that theaforementioned increase in solubility is due to the soluble complexbetween silver and hydantoin ring structures as it has been found thesilver remains soluble to a higher degree than expected.

The present invention has found that unhalogenerated hydantoins, such as5,5-dimethylhydantoin (DMH), also has the qualities to interact withmetal ion donors including silver metal ion donors such as silverbromide to increase the solubility of the silver bromide in a waterenvironment and aid in the disinfection process. That is, with a silverion donor in the presence of DMH, it has been discovered that thedissolved silver concentrations are higher than anticipated whencompared to a control solution without the presence of DMH. The resultssuggested that DMH interacts with silver to form a soluble complex evenif the source(s) of silver are from insoluble salts such as silverbromide, which in some cases may be derived from silver chloride.

The inventor has determined that the introduction of hydantoins to thebody of water that has been treated with Ozone and containing silver ionand bromide ions increases the solubility of extremely insoluble silverwhile suppressing the oxidization of the bromide by the Ozone to reduceor eliminate the production of undesired bromate. In order to verifythat the DMH interacts to increase the solubility of extremely insolublesilver, the following test was performed using either silver chloride orsilver bromide as the donor of metal ions in order to demonstrate theenhancement of a silver concentration in a body of water when DMH isused in combination.

Testing for Effect of Hydantoins on Silver

Two spas were used in performing three (3) tests to evaluate thepotential use of DMH to increase silver solubility in the presence ofalternative disinfection systems such as sodium bromide. The first spaused was a 125-gallon Marquis® brand triangle shaped spa having thedimensions 60″×60″×82″ with a height of 32″ and a water depth of 27″without bathers. This spa featured 13 jets and one pleated filtercartridge (Unicel® 5CH-502), having a filtration area of 50 square feet.The second spa was a 325-gallon Dimension One® brand spa having thedimensions 90″×90″×355″ with a water depth of approximately 25″ withoutbathers. The Dimension One® brand spa featured 32 jets and two pleatedfilter cartridges (Unicel® 7CH-975), each having a filtration area of 75square feet. Spa water was maintained between 100° F. (37.8° C.) to 104°F. (40° C.) and was circulated at least 2 hours daily.

In the each of the tests a reagent grade Dimethylhydantoin (DMH, CAS No.77-71-4) obtained from Aldrich® with a 97% purity was used. Aconcentration of 5 ppm (parts per million) DMH was selected because 5ppm was the amount of DMH that can be delivered in the existing KingTechnology, Inc. Spa Frog® Mineral Cartridge to a 600 gallon spa, thelargest volume for the cartridge was designed.

The source of silver ions was obtained from a King Technology Inc. SpaFrog® Mineral Cartridge, which was randomly selected from KingTechnology Inc.'s production inventories for use in these tests andinstalled into the in-line system on the spa. These mineral cartridgesrelease silver ions into the spa in the form of silver chloride.Although silver chloride is described above as providing for the sourceof silver ion, in the present embodiment the source of silver ion mayalso comprises pure silver, silver metals, silver alloy or somecombination thereof because of the recognized bactericidal, viricidal,and algaecidal properties of silver. The silver metals can be introducedas metallic, zero valence material, or as metal ions that can beintroduced into the water by dissolution of soluble metal salts, or bythe dissolution of the metal itself. For example, silver ion can beintroduced into the water through the dissolution of silver nitrate, orthrough the dissolution of metallic silver as the result of conversionto silver oxide and subsequent conversion of the oxide to more solublesilver species. Mixtures of different salts, or of salts with metallicmaterial, may be combined together to provide the necessaryconcentration of metal ions in the water.

In Spa Studies 1 and 2, a commercially available sodium bromidedisinfectant system (Rendezvous®) was used. With the Rendezvous®)bromine disinfectant system, the sodium bromide solution is oxidized bythe addition of potassium peroxymonosulfate.

For Spa Study 3, different sodium bromide disinfecting systems wereevaluated in two (2) phases. During the first phase, the commerciallyavailable sodium bromide oxidized by the sodiumdichloro-s-triazinetroine disinfectant known as Spa Essentials®Brominating Concentrate was used. For the second phase of the spa studyreagent grade sodium bromide salt and potassium peroxymonosulfate wasused.

Addition of DMH

During the study, the spa was filled with fresh water prior to theinitiation of each study and the water balanced according to TaylorTechnologies Pool & Spa Water Chemistry Manual. The pH was reducedthrough the addition of sodium bisulfate (pH Down Balancer, GLB,Alpharetta, Ga.) to a range from 7.2 to 8.0. After balancing the spawater the King technology, Inc. Spa Frog® Mineral Cartridge wasinstalled into the inline system of the spa and a source of bromine wasadded to the spa water.

In Spa Study 1 an amount of DMH was added to the spa water after seven(7) weeks of silver data had been collected to result in a finalconcentration of 5 ppm (parts per million). For Spa study 2, an amountof DMH was added to the spa water after three (3) weeks of silver datahad been collected to result in a final concentration of 5 ppm, and forSpa Study 3 an amount of DMH was added to the spa water after one (1)week of silver data had been collected to result in a finalconcentration of 5 ppm.

Sodium bromide or brominating concentrate (dichloro-striazinetrione plussodium bromide) was added to each spa during test intervals. Typically,sodium bromide was activated by oxidation to bromine with potassiumperoxymonosulfate. Alternatively, when the brominating concentrate(dichloro-striazinetrione plus sodium bromide) was used, the sodiumdichloro-s-triazinetrione oxidized the sodium bromide to make brominein-situ. Additional water was added to the spa when the water leveldropped below the skimmer water returns.

Water Testing

Chemical tests were performed with water samples obtained from each ofthe spas for levels of dissolved silver concentration, bromide, andchloride approximately once a week. Bromide was tested to provide ameans to calculate the theoretical silver concentration based on thesolubility product of silver bromide. Result of the test for bromide anddissolved silver concentration are shown in FIG. 1 for Spa Study 1, areshown in FIG. 2 for Spa Study 2, and are shown in FIG. 3 for Spa Study3.

Additionally, the spa water's total alkalinity, turbidity, and pH werealso tested and maintained within ranges accepted by the industry. Theideal pH for a spa is 7.20 to 7.60, however wider ranges are acceptable.In the studies, the average pH for Spa Study 1 was 7.51, Spa Study 2showed an average pH of 7.61, and Spa Study 3 had an average pH of 7.47.These three spa studies were maintained within the ideal pH for a spa.

The International Aquatic Foundation (ANSI/NSPI) recommends a level oftotal bromine to be between 2.0 and 4.0 ppm for residential spas with amax of 6.0 ppm. In the studies, the average total bromine concentrationmeasured for Spa Study 1 was 3.74 ppm, the average total bromineconcentration measured for Spa Study 2 was 656 ppm, and the averagetotal bromine concentration measured for Spa Study 3 was 3.58 ppm.

In regards to the level of silver ions, the King Technology, Inc. SpaFrog® Mineral Cartridge contains silver ions in the form of solid silverchloride (AgCl) distributed over a porous matrix. Water flowing throughthe matrix comes into contact with the silver chloride resulting in therelease of soluble silver ions to the water. DMH was also released intothe water resulting in the formation of ionic-hydantoin structures. Itwould be anticipated that soluble silver ions would be depleted from spawater through the formation of silver bromide, an insoluble salt.However, as shown in FIG. 1 for Study 1, after the DMH was added to thewater in the pool, the actual silver concentrations were higher than thecalculated theoretical silver concentration.

The result of Study 1 were further supported in Study 2 and Study 3,shown in FIGS. 2 and 3, which both show that after the DMH was added tothe water in the pool, the actual silver concentrations were higher thanthe calculated theoretical silver concentration. More specifically, oncemeasurable within reporting limits the average measured concentration ofdissolved silver for Spa Study 1 was 55 ppb. Spa Study 2 had an averagemeasured concentration of 5.33 ppb for dissolved silver and Spa Study 3had a measured concentration of dissolved silver of 32 ppb. Referring toFIGS. 1, 2, and 3, the highest observed silver concentration in each spastudy was, 7 ppb; 6 ppb, and 6.5 ppb, respectively.

Referring to FIGS. 1, 2, and 3, the results of the three spa studiesrevealed that before the addition of DMH, dissolved silver concentrationfor each of the studies were below the official reporting limit of 4.8ppb (parts per billion). However, around one to three weeks after theaddition of a concentration of 5 ppm DMH, silver concentrations in eachof the Spa Studies increased above the reporting limit, and weresignificantly higher than concentrations that would be anticipated basedon silver solubility calculations from silver bromide. The above resultsof Spa Studies 1, 2, and 3 thus supports the finding that thecombination of an unhalogenated hydantoin such as 5,5-dimethylhydantoinwith a metal ion donor such silver bromide enhances a concentration ofthe metal ions in the body of water by retaining or increasing thesolubility of metal ions from other metal ion donors to retain theantimicrobial activity of the metal ions in the water.

Effect of Hydantoins on Silver Interaction between Ozone and Bromide

In regards to the interaction between Ozone and bromide ion, themechanism for the interaction between Ozone and bromide ion has beenwell documented by W. R. Haag and J. Hoigne in the article titled“Ozonization of Bromide-Containing Waters: Kinetics of Formation ofHypobromous Acid and Bromate,” Environ. Sci. Technol., 17(5), 261, 1983.Referring to the Haag and Hoigne reaction mechanism, which is listedbelow, it is known that the presence of the bromide ion (Br⁻) in waterthat has been ozonized initially results in the formation of hypobromousacid (HOBr), which can function as a secondary biocide. That is, theprimary disinfection of the water is accomplished by Ozone, which killsthe initial microbial populations. The hypobromous acid then providesfor secondary disinfection by killing a lower microbial populationsacquired by the water after the initial disinfection of the water by theOzone

O₃+Br⁻====>HOBr+O₃========>O₂+OBr⁻  (1)

2O₃+OBr⁻========>2O₂+BrO₃ ⁻  (2)

As shown in step (1), the exposure of the hypobromous acid to Ozoneresults in the conversion of the hypobromous acid to hypobromite (OBr⁻)As shown in step (2), the exposure of the hypobromite (OBr⁻) to Ozoneresults in the conversion of the hypobromite (OBr⁻) to the highlyundesirable bromate ion (BrO₃ ⁻). On prolonged exposure to Ozone, allthe bromide ions will be converted to bromate.

In order to eliminate or reduce the formation of the bromate to a safelevel in the body of water, the Inventor has determined that theintroduction of small amounts of hypobromite ion (OBr⁻) scavengers tothe water being treated with Ozone and containing bromide ions andsilver ions for the purpose of disinfection will result in thesuppression of the second step of the Haag and Hoigne reaction mechanismthereby eliminating the formation of the bromate or at the very leastreducing the formation of the bromate to a safe level or safeconcentration.

In regard to the hypobromite ion scavenger, ideally the hypobromite ionscavenger should possesses a functional group that is capable ofintercepting OBr⁻ ions and preferentially forming some sort of biocidalderivatives. It has been determined that hydantoins such asdimethylhydantoin (DMH) in sufficient amount should be able to suppressthe second step of the Haag and Hoigne reaction mechanism, and morespecifically suppress the catalytic decomposition reaction of Ozone withhypobromite ions since DMH include the presence of an amide group thatwould be capable of intercepting the hypobromite ion (OBr⁻).

The amount of hydantoins required to suppress the catalyticdecomposition reaction of Ozone with hypobromite ions depends on thewater being treated and on the amount of bromide ions present. Anexample of one logical type of hydantoin that may be use as an OBr⁻ ionscavenger additive would be dimethylhydantoin (DMH) as DMH include thepresence of an amide group that would be capable of intercepting thehypobromite ion (OBr⁻). As such, the introduction of hydantoins to thebody of water that has been treated with Ozone and containing silver ionand bromide ions provides the dual purpose of (1) not only enhancing theconcentration of silver ion for water disinfection but also (2)suppressing the oxidization of the bromide by the Ozone to eliminate orreduce the production the bromate to a safe level for human use.

The present invention provides an enhanced method and system fortreating water that has been treated with Ozone and containing silverion and bromide ions. The additives of the present invention may bereadily used with existing ozonization systems. In addition, a sourcebromide ion, a source of silver ion and the hypobromite ion scavengeradditive may be provided as an admixture of the two compounds that maybe added to water presently being treated with Ozone alone. In regardsto the hypobromite ion scavenger additive, although hydantoins such asdimethylhydantoin (DMH) have been described in the present invention asbeing suitable hypobromite ion scavengers other additives containingimide and/or amide group similar to DMH may also be used to scavengeOBr⁻ ion, provided they were present at sufficiently highconcentrations.

An embodiment of the present invention includes a method for generatingstable residual disinfectants during the ozonization of water comprisingthe step of carrying out the ozonization of water in the presence ofbromide ions, silver ions and an effective amount of a hydantoin tothereby enhance the concentration of silver ions in the water whilesuppressing the catalytic decomposition reaction of Ozone withhypobromite ions.

A further embodiment of the present invention is an additive compositionfor generating secondary disinfectants during the ozonization of watercomprising an admixture of bromide ions, silver ions and a hypobromiteion scavenger that converts hypobromite ions to biocidal, Ozone-stablederivatives thereof to thereby suppress the catalytic decompositionreaction of Ozone with hypobromite ions to eliminate or reduce theproduction the bromate to a safe level for human use.

Referring to FIGS. 4 and 5, FIG. 4 shows an embodiment of an apparatusof the present invention comprising a dispenser 10 having a housing 11containing a compartment 12 therein. Located in compartment 12 is asource of DMH 13 and a bactericide comprising a silver ion donor such assilver bromide 14. A set of openings 15 allows water access tocompartment 12 and to the source of DMH 13 and the silver bromide 14.

FIG. 5 shows an alternative embodiment of an apparatus of the presentinvention comprising a dispenser 16 having a first housing 17 with acompartment 18, a second housing 19 with a compartment 20, and a thirdhousing 21 with a compartment 22 therein. Located in compartment 18 is asilver ion donor such as silver chloride 23, located in compartment 20is a source of DMH 24, and located in compartment 22 is a bromide iondonor such as sodium bromide 25. A set of openings 26 allows wateraccess to compartment 18 and to the silver chloride 23. A set ofopenings 27 allows water access to compartment 20 and the source of DMH24. Similarly, a set of openings 28 allows water access to compartment22 and the source of sodium bromide 25. Although FIGS. 4 and 5 show theuse of the silver ion donor as comprising silver bromide and silverchloride, other types of silver ion donors and other alternativebactericides whose solubility can be changed in the presence of DMH canalso be used. Similarly, although FIGS. 4 and 5 show the use of thebromide ion donor as comprising silver bromide and sodium bromide, othertypes of bromide ion donors may also be used.

In regards to the source of DMH 13, 24 of FIGS. 4 and 5, FIG. 5 showssource of DMH 24 in particles form with the aforementioned particleshaving an initial size that are larger than the size of opening 27 toprevent the DMH particles from escaping through openings 27. FIG. 4shows the source of DMH 13 in tablet form. Various types of materialincluding but not limited to microcrystalline cellulose (MCC) may beused as a binder in the formation of the DMH tablets which aretabletized with the metal ion donor so that both the DMH and the metalion donor can be placed in the body of fluid to be treated.

It is noted that the preferred level of the DMH present in the body ofwater is between 5 and 50 ppm with the DMH and the source of silvercooperating to maintain a level of silver ions present in the amount of1 to 3 ppb and/or alternatively cooperating to maintain a level ofsilver ions present to sustain a standard plate count at 35 degrees F.of less than 200 colonies per milliliter. The level of the DMH in thebody of water however may be higher than 50 ppm.

The present invention includes a method of treating an ozonized body ofwater in the presence of bromide ions to kill microorganisms byenhancing the metal ions concentration while eliminating or reducing theproduction bromate, the method comprising the steps of placing thedispenser 10, 16 containing the source of DMH 13, 24, a silver ion donor14, 23, and a bromide ion donor 14, 25 in the body of water and allowingwater that has been treated with ozone to come into contact with thesource of DMH 13, 24, the silver ion donor 14, 23, and the bromide iondonor 14, 25 to periodically release DMH, silver ions, and bromide ionsinto the body of water. As the DMH is released into the body of water,the DMH is carried to the silver ion donor 14, 23 and the bromide iondonor 14, 25 and interacts with the silver ion donor 14, 23 and thebromide ion donor 14, 25 to increase the solubility of the silver ions.That is, the DMH functions to allow for the release of more silver ionsinto the body of water and/or maintain the silver ions concentration inthe body of water at a higher of level than if the silver ion donor 14,23 were used alone in the body of water while suppressing the conversionof the bromide ions by the Ozone in the water to a bromate to render thewater for human use.

The present invention also includes a method of treating a body of waterto kill microorganisms by maintaining an effective concentration ofbiocides, the method comprising the steps of (1) treating the body ofwater with ozone; (2) adding a silver ion donor 14, 23 to the body ofwater; (3) adding a source of bromide 14, 25 to the body of water and(4) adding a concentration 5,5-dimethylhydantoin (DMH) 13, 24 to thebody of water to interact with the silver ion donor 14, 23 to maintain asilver ion concentration effective to kill microorganisms whilesuppressing the interaction between the ozone and the bromide ions toeliminate or reduce the production a bromate to a safe level for humanuse. The aforementioned method can also include the steps of (5) addingsilver chloride 14, 21 to the body of water; (6) adding silver bromideto the body of water (7) treating a body of recreational water for atleast partial human immersion therein; (8) placing a dispenser 10, 16containing both the silver salt 14, 21 and the 5,5-dimethylhydantoin 13,22 in the body of water and allowing water to come into contact withboth the silver salt 14, 21 and the 5,5-dimethylhydantoin 13, 22; and(9) adding silver chloride to the body of water on a carrier oflimestone.

I claim: 1.-11. (canceled)
 12. A dispenser for killing microorganisms ina body of water that has been treated with ozone in the presence ofbromide ions comprising: a first housing having a water accessiblecompartment containing a source of a hypobromite ion scavenger forreleasing the hypobromite ion scavenger when contacted by the body ofwater; and a second housing having a water accessible compartmentcontaining a metal ion donor for releasing metal ions when contacted bythe body of water.
 13. The dispenser of claim 12 including a thirdhousing having a water accessible compartment containing a bromide iondonor for releasing bromide ions when contacted by the body of water.14. The dispenser of claim 12 wherein the metal ion donor comprises aninsoluble metal ion donor.
 15. The dispenser of claim 12 wherein thesource of hypobromite ion scavenger comprises a hydantoin.
 16. Thedispenser of claim 12 wherein the source of hypobromite ion scavengercomprises 5,5-dimethylhydantoin.
 17. The dispenser of claim 12 whereinthe silver ion donor comprises silver bromide.
 18. The method of claim12 wherein the source of the hypobromite ion scavenger and the metal iondonor are in tablet form.
 19. The dispenser of claim 12 wherein themetal ion donor comprises silver chloride.
 20. The dispenser of claim 13wherein the first housing, the second housing, and the third housing arelocated in a dispenser having a set of openings for the ingress andegress of water into the compartments in the dispenser.